Specimen collection
Ca. assamicum plants with leaf spot were collected during the rainy season in 2012 form the organic farming field of the Defense Research Laboratory, Tezpur (district Sonitpur), which is located in the Assam state at 26 38'N and 92 48'E in northeastern India.Collected specimens were brought to the laboratory in sterile polythene bags. The leaves were cut from the margins of necrotic lesions(6-9 mm diameter) and each leaf piece with a necrotic lesions was divided into two parts. One part of the lesion was used for microscopic examination for presence of the fungal mycelium and spores and the remaining part was used for isolation of fungal phytopathogen.
The leaf parts with necrotic lesion were surface-sterilized with 1% sodium hypochlorite solution for 2 min, Followed by rinsing with sterilized distilled water twice to eliminate traces of the disinfectant.The surface-sterilized leaf tissues were placed on potato dextrose agar and incubated at 25 c.The emergent fungal growth was observed every 24 h for the next three day.